Grease composition



3,272,745 GREASE COMPOSITION James G. Dadura, Beacon, Norman R. Odell, Wappingers Falls, N.Y., and Paul A. Cantor, Covina, Calif., assignors to Texaco, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 27, 1%2, Ser. No. 247,549

7 Claims. (Cl. 252-33.6)

The present invention relates to lubricating grease compositions and, more particularly, to lubricating grease compositions having improved storage keeping properties.

It is known from US. 2,852,466 that grease compositions for high temperature applications can be prepared from oleaginous liquids such as, for example, hydrocarbon mineral oils and synthetic oils, containing as the thickening agent a metal salt of N-acylaminoorganocarboxylic acid, preferably the alkali metal and alkaline earth metal salts thereof. It is further known from US. 2,820,012 that high melting point grease compositions can be prepared from oleaginous liquids such as, for example, hydrocarbon mineral oils and synthetic oils, containing as the thickening agent a metal salt of N-phthalamic acid, preferably the lithium, sodium and barium salts of terephthalamic and isophthalamic acids.

In practice, the synthetic ester based grease compositions disclosed in these patents have been found to be deficient in storage stability, particularly with respect to unworked penetration values after storage for a relatively short period of time. This deficiency in storage stability seriously handicaps these greases in many applications, particularly for military use. For example, one MIL SPEC MIL-G-25760 requires a minimum penetration value of 200 on an unworked basis, after 6 months storage. These prior art type greases do not consistently meet this requirement in much shorter times, for example, after one or three months storage.

It has now been found that a specific combination of a particular class of grease thickening agents, the sodium salts of phthalamic acids or N-acylaminoorganocarboxylic acids, in a specific oleaginous base liquid exhibit unexpected advantages with respect to the storage stability properties of the resulting grease compositions.

According to the present invention, the grease compositions comprise a base fluid containing a major portion of benzyl alkyl (C -C branched chain) azelate and thickened to a grease consistency with a sodium salt of N-acyl para-amino-benzoic acid or a sodium salt of N-acyl phthalamic acid wherein the acyl group contains from about 14 to about 22 carbon atoms therein. In a particularly outstanding embodiment the alkyl group of the diester base oil contains 8 carbon atoms and the acyl group of the phthalamic acid thickening agent contains about 18 carbon atoms. In another particular embodiment the acid thickening agent is sodium-N-octadecyl-paminobenzoate.

It is surprising that the grease compositions of the present invention exhibit excellent storage stability properties, on an unworked basis, of 200 or more units penetration value, after 3 months storage, when other similar grease compositions do not exhibit such satisfactory storage stability values. More specifically, grease compositions using the thickener employed in the compositions of this invention, but having difierent ester base oils such as benzyltridecyl azelate, di-tridecyl sebacate, di-2-ethylhexyl sebacate or the complex ester oil obtained by reaction of sebacic acid, 1,3-hexanediol and Z-ethylhexanol, as the sole oil component or admixed with another oil such as a refined mineral oil, exhibit storage stability properties on an unworked basis below a value of 200, either immediately after preparation or in a relatively short period of time thereafter.

The grease compositions of the present invention com:- prise a benzyl alkyl (C C branched chain) azelate base oil containing the sodium salt of N-acyl-p-aminobenzoic acid or an N-acyl phthalamic acid, wherein the acyl group contains from about 14 to about 22 carbon atoms, in an amount sufficient to thicken said base oil to a grease consistency. In general, the composition may contain from about 51 to about of base oil wherein the benzyl alkyl azelate oil may be the sole oil component or admixed with other synthetic or mineral oils, and from about 10 to 49% of the acid salt thickening agent, based on the weight of the composition. The grease compositions of this invention usually also contain from about 0.5 up to about 5% by weight of a grease corrosion inhibitor and, in addition, may contain from about 0.5 to 5% by weight of an amine oxidation inhibitor.

As is understood in the grease art, the grease compositions may additionally contain minor amounts of conventional lubricity agents, coloring materials, extreme pressure agents and the like, including combinations thereof.

The benzyl alkyl azelate diester base oil can be employed as the sole oil component in the grease compositions of the present invention, or the diester oil can be employed in admixture with minor amounts of mineral and/ or synthetic oils, particularly other synthetic oils such as a silicone polymer oil, a polyether oil, a polyglycol oil, a polyester oil or mixtures thereof. A preferred base oil comprises a major p rtion of the benzyl alkyl azelate oil and a minor porti of a refined mineral lubricating oil, especially a med paraffin oil having a viscosity in the ra from about to 600 seconds, Saybolt Unii/ersal, at 100 F.

The alkyl portion of the diester base oil may be an isodecyl, isononyl, 2-ethylheptyl, isooctyl, 2-ethylhexyl, isoheptyl or isohexyl radical. It has been found that most satisfactory results are obtained when the alkyl radical is either isooctyl or Z-ethylhexyl.

A preferred lubricating grease composition comprises from about 38 to 78% by weight of benzyl isooctyl azelate, from 10 to 33% by weight of a refined mineral oil, from 10 to 25% by weight of the sodium salt of N-octadecylterephthalamic acid or N-octadecyl-p-aminobenzoic acid, as the thickening agent, and containing about l2% by weight of phenothiazine oxidation inhibitor and about 1-2% of N-cocoyl sarcosine corrosion inhibitor, wherein cocoyl refers to coconut oil acids.

Satisfactory arylamine oxidation inhibitors include diphenylamine, phenyl-alpha-naphthylamine, para-phenylenediamine and N-N'-diphenyl-para-phenylenediamine.

Satisfactory corrosion inhibitors include lead naphthenate and the sarcosines including the N-acyl sarcosines containing about 8 to about 20 carbon atoms in the acyl group, such as N-cocoyl sarcosine, N-lauryl sarcosine and N-stearyl sarcosine, wherein cocoyl represents coconut oil acids.

The grease compositions can be prepared by mixing together the base oil and the thickening agent and any additives used in the grease, employing any known mixing means, followed by milling in a colloid mill to obtain a thorough dispersion of the thickening agent in the oleaginous liquid.

Example 1 A grease was prepared by saponifying 288 parts by Weight of N-octadecylterephthalamic acid in 226 parts by weight of mineral oil A, a refined parafiin distillate oil having a 29.7 API gravity, a viscosity at 100 F. of 350 SSU, and a neutralization number of 0.03, using 25.1 parts of sodium hydroxide, at a temperature of 200 F. The mixture was heated to 325 F. with stirring and the synthetic ester base oil, benzyl isooctyl azelate,

was added thereto in an amount of 1000 parts by weight with continued stirring. The resulting stirred mixture was cooled to 200 F., 36.2 parts of phenothiazine oxidation inhibitor and 18.1 parts N-cocoyl sarcosine corrosion inhibitor were added, and the resulting mixture was intimately mixed. The penetration value of the mixed blend was adjusted at 200 F. to a value of 290 by the addition of 350 parts of benzyl isooctyl azelate. Thereafter the blend was milled once through a Premier Colloid Mill having a rotor-stator clearance of 0.002 inch.

The composition of the grease is shown in the table below.

Examples 2 and 3 Following the procedure described in Example 1 above other grease compositions were prepared in a similar manner using a mixture of benzyl isooctyl azelate and the complex ester formed by the reaction of sebacic acid with 1,3-hexanediol and 2-ethylhexanol. In Example 2, the grease was unmilled. In both of these examples the upper temperature limit was 400 F. The compositions of these greases are set forth in the table below.

Control examples A-F the grease compositions of the invention, particularly Examples 1 and 3, exhibit relatively little change on storage. In contrast, the worked penetration values of the control examples were substantially changed during comparable storage periods.

The data further illustrate the specificity of the base oils of the present invention, namely, the benzyl alkyl (C C branched chain) azelates, for the benzyl tridecyl azelate base oils do not exhibit satisfactory storage properties and the di-tridecyl sebacate oils are also unsatisfactory.

We claim:

1. A grease composition comprising 51 to 90% by weight of a benzyl C C branched chain azelate base oil thickened to a grease consistency with 10 to 49% by weight of a sodium salt of an acid selected from the group consisting of N-acyl p-aminobenzoic acid and N-acyl phthalarnic acid, said acyl group containing from about 14 to 22 carbon atoms.

2. A grease composition as claimed in claim 1 wherein the base oil comprises a mixture of benzyl isooctyl azelate and a minor amount of a refined parafiin distillate lubricating oil.

3. A grease composition as claimed in claim 1 wherein the thickening agent is sodium-N-octadecylterephthalamate.

4. A grease composition as claimed in claim 1 wherein the thickening agent is sodium-N-octadecylisophthalamate.

5. A grease composition as claimed in claim 1 wherein the thickening agent is sodium-N-octadecyl-p-aminobenzoate.

TABLE Examples 1 2 3 Component, wt. percent:

Na-N-octadeeyl terephthalamate... Na-N-octadecyl-p-aminobenzoate Phenothiazine. N -coeoyi sareosine Benzyl isooctyl azelate Benzyl tridecyl azelate. Di-tridecyl sebacate Di-2-ethy1liexyl sebacate Complex ester oil from reaction of sebaclc acid with 1,3-hexanedioi and 2-ethyl hexanol Mineral oil B Cab-O-Sil (finely divided silica).

STORAGE PROPERTIES *Converted to ASTM, A, cone, worker used.

Inspection of the data in the table above show that the N-acyl-p-aminobenzoate or N-acylphthalamate sodium salt thickened benzyl isooctyl azelate greases exhibited excellent unworked storage stability over a three month period. It is to be noted that in no instance did the unworked penetration values reach a value of 200 or less. In contrast, the control examples showed very poor unworked storage stability values well below 200 in almost all cases after only one months storage. All of the control examples exhibited unworked storage penetration values well below 200 after 3 months and two of them, Control Examples A and E, were below 100. The

data further show that the worked penetration values of 6. A grease composition as claimed in claim 1 comprising 38 to 78% by Weight of benzyl isooctyl azelate, 10 to 33% of a refined mineral oil, 10 to 25% of the sodium salt of N-octadecylterephthalamic acid, 1 to 2% of phenothiazine oxidation inhibitor, and 1 to 2% of N- cocoyl sarcosine corrosion inhibitor.

7. A grease composition as claimed in claim 1 comprising 38 to 78% by weight of benzyl isooctyl azelate, 10 to 33% of a refined mineral oil, 10 to 25% of the sodium salt of N-octadecyl-p-aminobenzoic acid, 1 to 2% of phenothiazine oxidation inhibitor and 1 to 2% of N-cocoyl sarcosine corrosion inhibitor.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Graves et a1 25256 Zimmer et a1. 25256 Zisman et a1 252-56 Ashbum et a1 25256 Glavis et a1. 25256 6 2,521,438 9/1950 Zimmer et a1. 252-56 2,820,012 1/1958 Hotten 252-33.6 2,852,466 9/1958 Hot-ten 25233.6 3,108,963 10/1963 Benge 25256 DANIEL E. WYMAN, Primary Examiner. I. VAUGHN, Assistant Examiner. 

1. A GREASE COMPOSITION COMPRISING 51 TO 90% BY WEIGHT OF A BENZYL C6-C10 BRANCHED CHAIN AZELATE BASE OIL THICKENED TO A GREASE CONSISTENCY WITH 10 TO 49% BY WEIGHT OF A SODIUM SALT OF AN ACID SELECTED FROM THE GROUP CONSISTING OF N-ACYL P-AMINOBENZOIC ACID AND N-ACYL PHTHALAMIC ACID, SAID ACYL GROUP CONTAINING FROM ABOUT 14 TO 22 CARBON ATOMS. 